3D Plot points as spheres instead of dots?

I've created a 3D animation using the plot3 function and a loop, which works well enough. Currently the points are plotted as dots, but I want them to be spheres. I don't see any way to do this is the current list of linespec options. Can this be done? Currently I'm just using 'r.' for a red dot, but would like it to be a red sphere instead.

Answer 1

[Tyler Morrison]

I know its's a lot later now, but here is the simple function I whipped up today:

function S = plotSpheres(x, y, z, r, color)

% Get current axes held state.
held = ishold;

% Hold the axes of the current plot so we append to it.
hold on

% Get how many points we are using and check the dimensions match.
Npts = numel(x);
assert(Npts == numel(y));
assert(Npts == numel(z));

% Divide the radius number. This helps keep it in the integer range.
r = r/100;

% Get the current axes scales. (Unforunately the spheres will stretch if
% the axes are resized later.)
ax = gca;
xscale = ax.XLim(2) - ax.XLim(1);
yscale = ax.YLim(2) - ax.YLim(1);
zscale = ax.ZLim(2) - ax.ZLim(1);

% Preallocate the graphics object array.
S = gobjects(Npts, 1);

% Loop through all the give points.
for i = 1:Npts
    
    % Make a unit sphere.
    [X, Y, Z] = sphere;
    
    % Scale and shift the sphere.
    X = X*r*xscale + x(i);
    Y = Y*r*yscale + y(i);
    Z = Z*r*zscale + z(i);
    
    % Plot the sphere.
    S(i) = surf(X, Y, Z);
    
    % Visualization settings.
    set(S(i), 'FaceColor', color); % Set color.
    set(S(i), 'EdgeColor', 'none'); % Hide edges (wireframe).
    set(S(i), 'FaceLighting', 'gouraud'); % Set fancy lighting.
end

% Return to the hold status that it initially had.
if held; hold on; else; hold off; end
end

Answer 2

[Chad Greene]

You might be able to do it with the bubblegum plot function on FEX.

Answer 3

[Chad Greene]

Another option using built-in commands:

[x,y,z] = sphere(30);
s1 = surf(x,y,z);
shading interp
hold on
axis equal
camlight
lighting phong
set(s1,'facecolor',[.98 .45 .02]);

[Aaron Mears]

What you've got there seems to be creating a sphere where its surface is the trajectory of my function. What I need is the sphere to have the center be the point that is being plotted I believe.

[Chad Greene]

Yes, you'll have to scale the size of the sphere to how big you want it. You scale the sphere by multiplying x, y, and z by some value to make it bigger or smaller. You'll also have to add some displacement dx, dy, and dz values to place the center of the sphere to wherever you want it.

[Aaron Mears]

I'm not really sure how it would correlate to how I've already set this up. This is what I am doing:

p = plot3(0,0,0,'r.',x(j),y(j),z(j),'b.',a(j),b(j),c(j),'g.',d(j),e(j),f(j),'y.','markersize',20);

That is in a for loop, among other things that plots the points as it goes through the loop. It doesn't hold each last position, so it gives the plot an animated look as it iterates through the loop. The first point in that code above is a fixed point, the others are functions specified elsewhere in the code that are time based. I don't understand how to take what you've posted and apply it to my function in a way that it converts the plotted point to a sphere.

Answer 4

[Walter Roberson]

After you have created whatever line you need with plot3() without a marker, use scatter3() to plot the markers. scatter3() with 'filled' creates filled spheres.

[Aaron Mears]

I think we may be misinterpreting the difference between circles and spheres. When using scatter3, it creates circles, filled if you specify filled. I'm looking to plot spheres, 3D in appearance, like pictured above, that are the point as it is plotted, like a planet if you will. My original code and scatter3, etc...all seem to make circles or dots. I don't know if there is miscommunication about what I'm looking for or not. I'm trying to be as clear as possible. I tried earlier what mr. green had posted above about the sphere, which did create a sphere like that, but I can't seem to figure out how correlate that to a point in space and basically build a sphere around that point, which I think mr. green is saying I need to do.

[Walter Roberson]

scatter3() creates spheres. They are not lighted or shaded but they are spheres.

If you want you can use

function SpheresAt(x,y,z,R)

    if ~isvector(x) || ~isvector(y) || ~isvector(z) || ~isvector(R) || length(x) ~= length(y) || length(x) ~= length(z) || (length(R) > 1 & length(x) ~= length(R))
      error('all inputs must be scalar or vector and compatible sizes')
    end

    if length(R) == 1
      R = repmat(R, length(x), 1);
    end

    NumSphFaces = 30;

    [SX,SY,SZ] = sphere(NumSphFaces);

    washeld = ishold();
    hold on;

    for K = 1 : length(x)
      surf(SX*R(K) + x(K), SY*R(K) + y(K), SZ*R(K) + z(K));
    end

    lighting phong

    if ~washeld
      hold off
    end

[Ben Ward]

They are not really spheres, more like circles that always face directly to the camera. If you have a marker that bisects a plane, the intersection shows up as a straight line. If they were spheres the intersection would not be straight. This behaviour is a bit unfortunate, because the markers are more easily obscured than they would be if truly spherical.

It wouldn't be a problem if it was possible to specify the orientation of the circles in 3D space (i.e. along the x, y or z axis).